With rising concentrations of CO₂ in the Earth's atmosphere causing
concern about climate change, many solutions are being presented to
decrease emissions. One of the proposed solutions is to sequester excess
CO₂ in geological formations such as basalt. The deep subsurface is known
to harbor much of the microbial biomass on earth and questions abound as to
how this deep life is going to respond to the injection of CO₂. Many studies
have used model microorganisms to demonstrate the ability of microbes to aid
in the safe, permanent sequestration of CO₂ in the subsurface. The objective
of this research is to characterize the microbial community present in the
basalts at the Wallula pilot carbon sequestration well prior to the injection of
CO₂ and then perform laboratory studies to determine how the native microbial
community will respond to carbon sequestration conditions. Six samples were
collected from the Wallula pilot well prior to the injection of CO₂ into the
system. The microorganisms in these samples were characterized by
pyrosequencing of 16S rRNA genes, revealing a community dominated by the
Proteobacteria, Firmicutes, and Actinobacteria. The organisms detected were
related to microbes known to metabolize hydrogen, sulfur, and single carbon
compounds. These microorganisms may be stimulated in formations located
at the fringe of the pool of injected CO₂. Laboratory studies revealed that the
native microbial community suffered a two order of magnitude loss of
population upon exposure to CO₂ under carbon sequestration conditions. The
community also shifted from being dominated by Proteobacteria prior to CO₂
exposure to being dominated by Firmicutes after exposure. Specifically, the
genus Alkaliphilus, which was previously undetected, appeared after CO₂
exposure and became dominant. The dominance of Alkaliphilus, along with
other rare organisms which did not compose a majority of the population prior
to the introduction of CO₂ to the system, indicates that members of the rare
biosphere may be better adapted to changing environmental conditions
specific to CO₂ sequestration than other indigenous cells. Thus, the rare
biosphere should be examined closely as part of any environmental study, as
these minority microorganisms may be the first indication of perturbation or
impact. / Graduation date: 2013
| Identifer | oai:union.ndltd.org:ORGSU/oai:ir.library.oregonstate.edu:1957/30362 |
| Date | 15 June 2012 |
| Creators | Lavalleur, Heather J. |
| Contributors | Colwell, Frederick S. |
| Source Sets | Oregon State University |
| Language | en_US |
| Detected Language | English |
| Type | Thesis/Dissertation |
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